Electric switch



R. N. 'RowE ELECTRIC SWITCH Dec. 14, 1937.

Filed May 9, 1956 3 Sheets-Sheet l Raymond/K30? INVENTOR A TTORNEY R. N.ROWE ELECTRIC SWITCH Dec; 14, 1937.

3 Sheets-Sheet 2 Fi\led May 9, 1936 lNVENTOR I ATTORNEY Dec. 14, 1937.ROWE 2,102,545

ELECTRIC SWITCH v Fild May 9, 1935 5 Sheets-Sheet s Raymond A. RoweINVENTOR Patented Dec. 14, 1937 UNITED STATES PATENT OFFICE ELECTRICSWITCH necticut Application May 9, 1936, Serial No. 78,818

x 11 Claims.

My invention relates to circuit breakers and more particularly to animproved circuit breaker of the type utilizing the principle of selfcompression arc interruption. In circuit breakers utilizing thisprinciple, advantage is taken of two factors, namely, (1) that whencontacts are separated under load or short-circuit an arc is drawn in anatmosphere composed of air, metal vapors 'and some gas from insulationsurfaces, and (2) that the heat from the arc raises these gases to ahigh temperature. It is a known practice to seal the contacts in arelatively small chamber so that the expanding heated gases will createa high pressure in the area of the arc. This pressure increase offers animpediment to the flow of current through the arc area and the arc willthus be quenched or interrupted.

The primary object of the present invention is to produce an eflicientand eifective circuit breaker of the compression arc interruption type.

The use of this principle of arc interruption is comparatively easy ofaccomplishment when the moving contacts have a straight plunger motionor are carried by a rotatable shaft. In these cases the entrance of themoving contact into the compression chamber is sealed by suitablepacking around the reciprocating or rotating part. However, if themoving contact has an arcuate motion or has a movement in two dimensionsrelative to the plane of the stationary contact, as is often the case insome designs of switches equipped with circuit breakers, it is notpossible to make an effective seal of the moving contact within thecompression chamber.

A special object of my invention is to make a compression arcinterrupter adapted for use with any of the above described movements ofcontacts.

A still further object is to increase the safety factor in circuitbreakers for electrical systems.

Another object is to reduce fire hazard in the use of circuit breakers.

Another object is to' produce a novel and effective seal between thecontact parts and the switch operating handle in switches and circuitbreakers.

Another object is to decrease the physical dimensions of circuitbreakers, thus facilitating their use instead of the present fuses insystems already installed.

The accomplishment of these and other objects is brought about byenclosing not only the contacts but also the entire switch and circuitbreaker tripping mechanisms within a sealed meeting a certain set ofrequirements, then the casing. Thus the casing for the parts acts as acompression chamber.

In order to accomplish the desired result it is necessary both to sealthe casing and to make the sealed chamber sufficiently small so that theexpanding gases will build up an effective are interrupting pressure.This is necessary because high temperature gas is not ordinarilyconsidered a good medium to stop an arc.

The compression chamber must be small enough so that, with a givenspacing of arcing contacts, sufiicient pressure will be built up by theexpanding contained gases to quench rapidly any are which is formed bythe extra potential in the breaker. The necessary size of thecompression chamber, for any given distance of contact separation andany given impressed voltage, may be determined experimentally. When thisdesired restriction of volume has been ascertained for switch andcircuit breaker mechanisms must be built in such a manner as to comewell within the volume required. Of course, the switch parts themselveswill diminish the volume of the gases in the chamber when the parts arein place.

Because the switch handle must, in most intances, extend outside of thecasing, special provision is made for sealing the handle. This seal ismade both internally and externally of the casing, thus providing astronger as well as a more efi'icient structure.

Finally, the casing must be made strong enough to withstand thepressures built up by the are. This is done by making heavy walls,preferably of rag bakelite, and securing the parts of the casingtogether at a number of balanced spaced points. The handle seal isprovided with an internal plate of metal to insure further strength atthis portion of the compression chamber.

A more detailed description of one form of my 40 invention-is givenbelow, and should be read in connection with the accompanying drawingsin which:

Fig. 1 is a longitudinal partial sectional view of one form of myinvention, the compression chamber being shown in section and a combinedswitch and circuit breaker in elevation. The parts are in ofi position.

Fig. 2 is a view similar to Fig. 1, showing the switch and circuitbreaker parts in section. the parts being in on" position. 7

Fig. 3 is a sectional View of the switch and circuit breaker parts intripped position.

Fig. 4 is an external perspective view of a complete device according tomy invention.

Fig. 5 is a plan view of the device as shown in Fig. 2, with the toppart of the compression chamber and the switch handle members removed.

Fig. 6 is a vertical section substantially on the plane of line 6--6 ofFig. 4.

' slightly modified form of casing and seal.

In these drawings, the compression chamber and casing is formed of a toppiece ii] and a base ll, both of proper weight and strength to withstandsafely the pressures involved. I prefer to mould these parts of ragbakelite, a phenolic condensation product which is reinforced with ragscraps.

The two parts of the casing are firmly held together by any suitablemeans, such as the four screws 82, which pass through bores in the toppiece and threadedly engage the base. These screws are located at evenlyspaced points, such as the corner portions of the case, so that allsides are held under pressure. If desired, a further sealing of theparts may be obtained through the use of interfitting shoulder or stepportions l3. Cement, shellac, or other adhesive may be used if desired,to insure a good seal between the casing parts.

Located outside of the casing wall is a line terminal binding screw Mand a load terminal binding 'screw i5, shown as threadedly engaging aline terminal contact plate It and a load terminal connection plate l'lrespectively. These plates are snugly and securely surrounded by thecasing where they pass into the compression chamber. A stationarycontact piece it is secured to the inner end of plate is.

At I9 is indicated the interior compression chamber which also containsthe switch and circuit breaker parts. A switch yoke piece 28 is pivotedwithin the chamber l9.

On the outside of the casing at M is a convex surface with a radius ofcurvature centered at the pivot point of switch yoke 20. A switch handle22, preferably of insulating material, closely fits and rides on theconvex surface 2!.

A screw 23 passes through the handle and threadedly engages an aperturein the top of yoke piece to hold the handle close against the convexsurface. This screw passes through a slot 24 in the casing wall, theslot being long enough to permit movement of the handle to on and offpositions, but being only slightly wider than the diameter of the screw23. Arcuate flanges 25 on the handle close the slot 24 at all times, thehandle and flanges being wide enough to extend well beyond all edges ofthe slot.

At 26 is a concave wall in the chamber 59, with a radius of curvaturecentered on the pivot point of the yoke 20. A sealing and reinforcingplate 21, preferably of metal or other strong material, closely fits andrides in this concavity, the screw 23 freely passing through this platealthough closely surrounded thereby. A spring 28, between the plate 21and yoke 20, presses the plate into engagement with the wall 26 to sealthe slot 24 at all times.

Within the chamber is mounted an'ap lopriate switch and circuit breakermechanism. Al-

tro-responsive trip device, such as a magnetic trip, might besubstituted. The prime desideratum is to make these parts small enoughso that the compression chamber is of a size to function properly.

The novel compact structure illustrated in-- cludes a switch frame 29which has vertical side portions 30 and M. The yoke 20, mentioned above,straddles these frame sides and is provided with rounded ends 32 whichbear in suitable depressions in the bottom of the chamber to pivot theyoke.

A switch throw piece 33 is pivotally connected to the switch frame sidesby a pivot pin 34. At the free end of the piece 33 is suitably mountedan insulation block 35, carrying the pin catch 36. This pin may be screwthreaded for adjusting or calibrating the trip action of the mechanism.Ears 3? on yoke 29 and a pin 38 through throw piece 33 are connected bymeans of springs 39.

On the same pivot 34 as the switch throw piece is mounted the trippiece- 40, having side arms fill which support a flexible, resilient,current carrying bar 62. This bar has a contact 43which is adapted toengage stationary contact l8 when the switch is on. The free end of bar42 is normally'in the path of arcuate movement of catch pin 36. This endof the bar is also connected at 34 to a flexible lead which in turn isconnected as at $6 to the inner end of the load terminal plate l7.

A spring 58 is connected between the trip piece ill and a projecting arm69 on the switch frame to urge this trip piece toward circuit breakingposition.

Stops in the form of lugs on the frame 29 limit the extent of movementof yoke piece 20. At St are illustrated screws for holding the switchframe in place within the chamber.

Assuming the switch and breaker parts to be in the position of Fig. 1,in order to close the switch the handle 22 is moved to the left. Theyoke 20 is also moved to the left and the springs 39, when past thecenter point, pull the throw piece 33 over. Pin catch 36 engages thefree end of bar 42 and pushes trip piece (against the action of spring48) so that contact 43 engages stationary contact I8. The parts are thenin the position of Fig. 2.

The switch is thrown off by a reverse movement of the handle whereby theyoke, springs 38, and throw piece 33 move back and trip piece 40 ispushed back by engagement with the insulating block 35. The spring 48aids in this return movement of the trip piece 40.

When the switch is on, current goes through terminal l6, contacts I8 and43, bar 42 (with its bimetallic piece 47), connection 44, cable 45,connection 46, and load terminal Ill. On an overload or short circuitthe bimetallic element 41 becomesheated and flexes upwardly, lifting thefree end of bar clear of the end of catch pin Spring 48' then pulls thetrip piece 40 to disengage contact 43 from contact l8. The other partsof the device remain in substantially the same position. See Fig. 3. Aslong as the bimetallic bar is flexed, the switch is trip free, that is,the circuit cannot be'switched or held on" until the electro-responsivemeans returns to normal.

To reset the device, after the bimetallic element has been allowed tocool, it is merely necessary to throw the handle to off position, whenthe yoke will move springs 39 to pull the throw piece 33 back. The endof pin 36 will slide under and slightly flex the end of bar 42 untildestroyer.

the pin passes behind the end of the bar to the position shown inFig. 1. The switch may then be thrown on as before.

When the switch is in either the oil or tripped position the walls ofchamber l9 act as stops for the contact end of element 40 and the catchend of element 33.

By the above described structure I have provided an extremely eilicient,simple, and compact circuit breaker. The small size of the chamberpermits the use of the compression arc interruption principle and doesaway with expensive auxiliary arc quenching mechanisms. The switchcasing and are quenching medium are one and the same. No matter whatform of movement the contact may make in breaking the circuit, the onlyseal necessary around a moving part is the simple one at the handle.

The close fit of the casing parts with one another and with the terminalpieces means not only a good seal for compression arc interruption butalso entirely eliminates any flash from the are outside of the casing.The handle structure is also incidentally effective as a fire hazardThere are absolutely no vents in the casing.

Besides strengthening one wall of the chamber and making a seal at thatwall, the switch handle reinforcing plate inside of the chamberautomatically increases its sealing effect when pressure is built up inthe chamber. Internal pressure tends to make this plate adhere even moreclosely than usual to the inside wall. In spite of this, no added strainis thereby put on either the switch handle or internal mechanism.

Another result of this structure is to materially reduce the size ofcircuit breakers, making them more easily adaptable in places wherefuses were formerly used.

In Fig. 9 I have shown a slightly modified form of compression chambercasing in which H8 is the top piece; III, the base; and. H3, a gasket ofrubber or other suitable material. This casing has the interior chamberN9, the convex outer surface Hi, the handle slot Hi, and other partssimilar to the form previously described. The casing parts, and thegasket, form 'a tight seal with each other and around the terminalmembers l6 and H asin the first form I I claim:

1. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber being such that the entrapped gases,when heated by the are drawn between said contacts on heavy overload,will expand and create pressure suflicient to extinguish the are rapidlywithout the assistance of any escaping gas, that improvement whichincludes a switch mechanism for moving said contacts into and out ofengagement with each other mounted entirely within said compressionchamber, electro-responsive means for opening said switch mechanism uponoverload -of said chamber, and seal ng also mounted entirely within saidchamber, and means for actuating said switch mechanism, said actuatingmeans being manipulative from outside of said chamber, and meanspreventing the escape of gas under pressure from said casing at thelocation of said actuating means.

2. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume and strength of said chamber being such that theentrapped gases, when heated by the are drawn between said contacts onsubstantially short circuit conditions, will expand and create pressuresufiicient to extinguish said are rapidly without the assistance of anyescaping gas, that improvement which includes a means for moving saidcontacts into and out of engagement with each other mounted entirely,within said compression chamber, electro-responsive .means also mountedentirely within said chamber for opening said switch mechanism byrelatively moving said contacts out of engagement with each other, andmeans for resetting said electro-responsive means, said resetting meansbeing manipulative from outside of said chamber, and means preventingthe escape of gas under pressure from said casing at the location ofsaid resetting means.

3. In a circuit breaker of the type having a sealed compression chamberof molded electric insulating material and contacts movable relative toone another located within said chamber, the volume and strength of saidchamber being such that the entrapped gases. when heated by the aredrawn between said contacts on heavy overload. will expand and createpressure alone sufficient to extinguish said are rapidly, thatimprovement which includes a switch mechanism for moving sa d contactsinto and out of contact with each other mounted ent rely within saidcompression chamber. electro-resnonsive means also mounted entirelywithin said chamber for opening said switch mechanism by relativelymoving sa d contacts out of engagement with each other, and a handle foractuating said switch mechanism, said handle extending outside meanspreventing the escape of gas under pressure from said casing at thelocation of said handle.

4. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber be ng such that the entrapped gases,when heated by the arc drawn between said contacts, will expand andcreate pressure sufiicient to extinguish said are rapidly, theimprovement which includes a switch mechanism for moving the contactsinto and out of engagement with each other and mounted substantiallyentirely within the cornpression chamber, electro-responsive means alsomounted substantially entirely within sa d chamher for separating saidcontacts, a handle slidable along a longitudinal slot in said chamberfor actuating said switch mechanism, a sealing plate separately andyieldably mounted with respect to said handle held against the inside ofsaid chamber and extending acrosssaid slot when the handle is inposition with the contacts closed, said sealing plate being pressedagainst the inside of the chamber around said slot to close the slot onthe generation of pressure within the chamber, said handle extendingthrough the sealing plate.

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5. In a circuit breaker of the. type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber being such that. the entrappedgases, when heated by the are drawn between said contacts, willexpandand create pressure sufflcient to extinguish said are rapidly, theimprovement which includes a switch mechanism for moving the contactsinto and out of engagement with each other and mounted substantiallyentirely within'the compression chamber, electro-responsive means alsomounted substantially entirely within said chamber for separating saidcontacts, a handle slidable along a longitudinal slot in said chamberfor actuating said switch mechanism, a sealing plate held against theinside of said chamber and extending across said slot when the handle isin position with the contacts closed, said sealing plate being pressedagainst the inside of the chamber around said slot to close the slotonthe generation of pressure within the chamber, said handle extendingthroughv the sealing plate, and flanges on said handle closing said sloton the outside of the chamber. 4

6. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber being such that the entrapped gases,when heated by the are drawn between said contacts, will expand andcreate pressure sufiicient to extinguish said are rapidly, theimprovement which includes a switch mechanism for moving the contactsinto and out of engagement with each other and mounted substantiallyentirely within the compression chamber, electro-responsive means alsomounted substantially entirely within said chamber for separating saidcontacts, a handle slidable along a longitudinal slot in said chamberfor actuating said switch mechanism, a sealing plate held against theinside of said chamber and extending across said slot when the handle isin position with the contacts closed, said sealing plate being pressedagainst the kinside of the chamber around said slot to close'the slot onthe generation of pressure within the chamber, said handle extendingthrough the sealing plate, said sealing plate being of metal resilientlyheld against the inside of the chamber and movable with the handle.

'7. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber being such that the entrapped gases,when heated by the against the inside of said chamber and extendingacross said slot when the handle is in position with the contactsclosed, said sealing plate being pressed against the inside of thechamber around said slot to close the slot on the generation of pressurewithin the chamber, said handle extending through the sealing plate,said sealing plate being of metal resiliently held against the arcadesinside ofthe chamber and movable with the handle, and non-metallicflanges on the handle closing said slot outside of the chamber.

8. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber being such that the entrapped gases,when heated by the are drawn between said contacts, will expand andcreate pressure sumcient to extinguish said are rapidly, the improvementwhich includes a switch mechanism for moving the contacts into and outof engagement with each other and mounted substantially entirely withinthe compression chamber, electro-responsive means also mountedsubstantially entirely within said chamber for separating said contacts,a handle for actuating said switch mechanism and extending out of thechamber, sealing means around said handle where it passes out of thechamber to check the escape of gas from the chamber, a springcooperating with said handle and sealing means for pressing said sealingmeans against the inside of said chamber, said switch mechanism being ofthe type in which said contacts are moved in and out of engagement by atleast one of the contacts having an arcuate motion.

9. In a circuit breaker of the type having a sealed compression chamberand contacts movable relative to one another located within saidchamber, the volume of said chamber being such that the entrapped gases,when heated by the arc drawn'between said contacts, will expand andcreate pressure sufiicient to extinguish rapidly said arc, thatimprovement which includes a switch mechanism for moving said contactsinto and out of contact with each other mounted entirely within saidcompression chamber, electroresponsive means also mounted entirelywithin said chamber for separating said contacts, a handle extendingthrough and movable along an elongated slot in said chamber, a sealingplate yieldably mounted on said handle and closing said slot on theinside of the chamber, a portion of the chamber wall transversely oneach side of berwalls which are thicker than said thin mrtion, saidhandle extending through and being movable with said sealing plate.

10. A circuit breaker having walls of electrically insulating materialforming a gas-tight compression chamber, a stationary and a movablecontact in said chamber, snap action operating means for said movablecontact mounted in said chamber, an elongated opening in one wall ofsaid chamber, a handle for said operating means extending through saidopening, a pivoted support for said handle in said chamber, a sealingplate carried by said handle cooperating with an inner surface of saidwall adjacent said opening so as to seal said chamber gas-tightly whensaid handle is in a position to move said movable contact intoengagement with said stationary contact, said walls defining a chamberhaving arelatively small volume such that the air entrapped at aboutat-= mospheric pressure in said chamber is heated byber, stationary andmovable contacts within said chamber, snap action means forautomatically operating said movable contact to open the circuit onoverload, a handle pivoted in said. chamher for operating said movablecontact and ex- 'tending out of the chamber through a slot, a

said slot to seal the chamber against escape of gas, said chamber beingnarrow and small enough to allow and strong enough to Withstand gaspressure generated by an are under heavy overload or substantially shortcircuit to quench the are substantially solely by said gas pressure.

RAYMOND N. ROWE.

